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coreos-base/oem-ec2-compat: use ttyS0 for console #2189

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@crawford crawford commented Sep 14, 2016

On HVM instances, tty0 is actually a graphical interface. Since the
interface exposed is non-interactive, it's not possible to scroll
through the logs, which results in lots of missing information. Setting
the console to ttyS0, on the other hand, sends the output to the system
log.

PV instances don't have this issue since they are xen-based and use
hvc0.

@@ -5,3 +5,7 @@ set oem_id="ec2"
# Blacklist the Xen framebuffer module so it doesn't get loaded at boot
# Disable `ens3` style names, so eth0 is used for both ixgbevf or xen.
set linux_append="modprobe.blacklist=xen_fbfront net.ifnames=0"

if [ "$grub_platform" = pc ]; then
set linux_console="console=ttyS0,115200n8"

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@marineam

marineam Sep 14, 2016
Contributor

Add grub serial so you see it's output too:

      serial com0 --speed=115200 --word=8 --parity=no

 terminal_input console serial_com0
 terminal_output console serial_com0

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@crawford

crawford Sep 14, 2016
Author Member

That's an unfortunate side-effect. Added.

@crawford crawford force-pushed the crawford:ec2 branch from 2bdd34c to 2873b03 Sep 14, 2016
@@ -5,3 +5,10 @@ set oem_id="ec2"
# Blacklist the Xen framebuffer module so it doesn't get loaded at boot
# Disable `ens3` style names, so eth0 is used for both ixgbevf or xen.
set linux_append="modprobe.blacklist=xen_fbfront net.ifnames=0"

if [ "$grub_platform" = pc ]; then
set linux_console="console=ttyS0,115200n8"

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@marineam

marineam Sep 14, 2016
Contributor

Very intentional, if the config has customized the linux console it is responsible for configuring grub too.

Oh, but you can actually drop console, so grub also doesn't do the dual output, only writing to serial_com0

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@marineam

marineam Sep 14, 2016
Contributor

So forcing you to configure grub actually makes grub behave correctly too! :-P

On HVM instances, tty0 is actually a graphical interface. Since the
interface exposed is non-interactive, it's not possible to scroll
through the logs, which results in lots of missing information. Setting
the console to ttyS0, on the other hand, sends the output to the system
log.

PV instances don't have this issue since they are xen-based and use
hvc0.
@crawford crawford force-pushed the crawford:ec2 branch from 2873b03 to a89f6ae Sep 14, 2016
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@marineam marineam left a comment

LGTM

@crawford crawford merged commit 7efd3ca into coreos:master Sep 14, 2016
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@crawford crawford deleted the crawford:ec2 branch Sep 14, 2016
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